1. Field of the Invention
The present invention pertains to endless belts comprising a load carrier cord, and particularly to such belts wherein the cord comprises a plurality of fibers of para-aramid and a second polymer.
2. Description of Related Art
In the construction of endless belts and other rubber composite articles employing a load-carrying cord comprising a plurality of yarns, it is known to utilize high strength fibers to form the cords. In such constructions intended for use in automotive and some industrial applications for example it is known to utilize such materials as para-aramid, polyethylene naphthalate (PEN) and poly-p-phenylene benzobisoxazole (PBO) as the fiber from which the load carrier cords are formed.
Particularly but not exclusively in the area of multi-V-ribbed belts, synchronous or toothed belts and V-belts for utilization in automotive applications, including modern multi-function automotive applications such as electromechanical drives, the performance requirements for both the belt's flexural fatigue resistance and its load carrying capability have increased dramatically. Higher modulus cords, including those formed of PEN, PBO and para-aramid, have been identified for such purposes due to their high load carrier capability but are known to exhibit relatively poor flexural fatigue resistance. Attempts have been made to improve the flexural fatigue resistance of belts formed from such cords, e.g., by manipulating the configuration of the cords by utilizing for example braided cord instead of plied cord or increased twist level of the cord; but such methods generally increase production costs, and tend to decrease the overall cord strength and modulus, thereby diminishing the materials' usefulness.
The need remains for a load carrier cord, including for incorporation in an endless belt or similar rubber composite article, which exhibits a good balance of load carrying capability and flexural fatigue resistance.